Agreement No. CE 63/2016 (EP)

Environmental Monitoring and Audit
for Disposal Facility to the East of Sha Chau (2017-2020) - Investigation

MONTHLY EM&A REPORT FOR December 2019

 

Contents

1.1                   Background                                                             

1.2                   Reporting Period                                                   

1.3                   Details of Sampling and Laboratory Testing Activities   

1.4                   Details of Outstanding Sampling and/or Analysis    

1.5                   Brief Discussion of the Monitoring Results for ESC CMP V      

1.6                   Activities Scheduled for the Next Month 

1.7                   Study Programme                                                  

Annexes

Annex A       Sampling Schedule

Annex B       Water Quality Monitoring Results

Annex C       Graphical Presentations

Annex D       Dredging Record

Annex E       Study Programme

 

1.1                                Background

1.1.1                     The Civil Engineering and Development Department (CEDD) is managing a number of marine disposal facilities in Hong Kong waters, including the Contaminated Mud Pits (CMPs) to the South of The Brothers (SB) and to the East of Sha Chau (ESC) for the disposal of contaminated sediment, and open-sea disposal grounds located to the South of Cheung Chau (SCC), East of Tung Lung Chau (ETLC) and East of Ninepins (ENP) for the disposal of uncontaminated sediment.  Two Environmental Permits (EPs), EP-312/2008/A and EP-427/2011/A, were issued by the Environmental Protection Department (EPD) to the CEDD, the Permit Holder, on 28 November 2008 and 23 December 2011 for the Dredging, Management and Capping of Contaminated Sediment Disposal Facilities at ESC CMP V and SB CMPs, respectively.

1.1.2                     Under the requirements of the two EPs for ESC CMP V and SB CMPs, EM&A programmes which encompass water and sediment chemistry, fisheries assessment, tissue and whole body analysis, sediment toxicity and benthic recolonisation studies as set out in the EM&A Manuals are required to be implemented.  EM&A programmes have been continuously carried out during the operation of the CMPs at ESC and SB.  A review of the collection and analysis of such environmental data from the monitoring programme demonstrated that there had not been any adverse environmental impacts resulting from disposal activities ([1])([2]).  The current programme will assess the impacts resulting from dredging, disposal and capping operations of CMP V as well as capping operations of SB CMPs.

1.1.3                     The present EM&A programme under Agreement No. CE 63/2016 (EP) covers the dredging, disposal and capping operations of the ESC CMP V as well as the capping operations of the SB CMPs (see Annex A for the EM&A programme).  The scheduled EM&A programme for SB CMPs was completed in December 2018.  Detailed works schedule for ESC CMP V is shown in Figure 1.1.  In December 2019, dredging of accumulated natural deposits at ESC CMP Vb and disposal of contaminated mud at ESC CMP Vd were undertaken.

 

Figure 1.1      Works Schedule for ESC CMP V

1.2                                Reporting Period

1.2.1                     This Monthly EM&A Report for December 2019 covers the EM&A activities for the reporting month of December 2019.

1.3                                Details of Sampling and Laboratory Testing Activities

1.3.1                     The following monitoring activities were undertaken for ESC CMP V in December 2019:

             Water Column Profiling of ESC CMP Vd;

             Cumulative Impact Sediment Chemistry of of ESC CMPs;

             Pit Specific Sediment Chemistry of ESC CMP Vd; and

             Water Quality Monitoring During Dredging of ESC CMP Vb.

1.4                                Details of Outstanding Sampling and/or Analysis

1.4.1                     No outstanding sampling remained for December 2019. 

1.5                                Brief Discussion of the Monitoring Results for ESC CMP V

1.5.1                     Brief discussion of the monitoring results of the following activities for ESC CMP V is presented in this Monthly EM&A Report for December 2019:

             Water Column Profiling of ESC CMP Vd in December 2019;

             Cumulative Impact Sediment Chemistry of of ESC CMPs in December 2019;

             Pit Specific Sediment Chemistry of ESC CMP Vd in December 2019; and

             Water Quality Monitoring During Dredging of ESC CMP Vb in December 2019.


1.5.2                           Water Column Profiling of ESC CMP Vd December 2019

1.5.3                     Water Column Profiling was undertaken at a total of two sampling stations (Upstream and Downstream stations) on 12 December 2019.  The monitoring results have been assessed for compliance with the Water Quality Objectives (WQOs) set by Environmental Protection Department (EPD).  This consists of a review of the EPD routine water quality monitoring data for the dry season period (November to March) of 2009 - 2018 from stations in the Northwestern Water Control Zone (WCZ), where the ESC CMPs are located ([3]).  For Salinity, the averaged value obtained from the Reference (Upstream) station was used for the basis as the WQO.  Levels of Dissolved Oxygen (DO) and Turbidity were also assessed for compliance with the Action and Limit Levels (see Table B1 of Annex B for details).

In-situ Measurements

1.5.4                     Analyses of results for December 2019 indicated that levels of Salinity, pH and DO complied with the WQOs at both Downstream and Upstream stations (Table B2 of Annex B).  Levels of DO and Turbidity at all stations complied with the Action and Limit Levels (Tables B1 and B2 of Annex B).

Laboratory Measurements for Suspended Solids (SS)

1.5.5                     Analyses of results for December 2019 indicated that the SS levels at both Downstream and Upstream stations were complied with the WQO and the Action and Limit Levels (Tables B1 and B2 of Annex B).   

1.5.6                     Overall, the monitoring results indicated that the mud disposal operation at ESC CMP Vd did not appear to cause any deterioration in water quality during this reporting period.

1.5.7                           Cumulative Impact Sediment Chemistry of ESC CMPs December 2019  

1.5.8                     Monitoring locations for Cumulative Impact Sediment Chemistry for ESC CMPs are shown in Figure 1.2.  A total of nine (9) monitoring stations were sampled on 3 and 5 December 2019.

1.5.9                     Analyses of results for the Cumulative Impact Sediment Chemistry Monitoring indicated that the concentrations of most inorganic contaminants were below the Lower Chemical Exceedance Levels (LCEL) at most stations in December 2019, except concentrations of Arsenic were higher than the LCEL at Near-field station ESC-RNB, Mid-field stations ESC-RMA and ESC-RMB, Far-field station ESC-RFB and Ma Wan station (Figures 1 and 2 of Annex C). 

1.5.10                   Whilst the average concentration of Arsenic in the Earths crust is generally ~2mg/kg, significantly higher Arsenic concentrations (median = 14 mg/kg) have been recorded in Hong Kongs onshore sediments ([4]).  It is presumed that the natural concentrations of Arsenic are similar in onshore and offshore sediments ([5]), and relatively high Arsenic levels may thus occur throughout Hong Kong.  Therefore, the LECL exceedances of Arsenic are unlikely to be caused by the disposal operations at ESC CMP Vd but rather as a result of naturally occurring deposits. 

1.5.11                   For organic contaminants, the concentrations of Total Organic Carbon (TOC) varied between stations in December 2019, with the generally higher concentrations of TOC recorded at Capped Pit station ESC-RCA (Figure 3 of Annex C).  The concentrations of Tributyltin (TBT) were generally similar across stations, except at Ma Wan Station where higher concentrations were recorded (Figure 4 of Annex C).   The concentrations of Low Molecular Weight and High Molecular Weight Polycyclic Aromatic Hydrocarbons (PAHs) were below the LCEL at all stations in December 2019 (Figure 5 of Annex C).  Total Polychlorinated Biphenyls (PCBs), Total dichloro-diphenyl-trichloroethane (DDT) and 4,4-dichlorodiphenyldichloroethylene (DDE) concentrations were below the limit of reporting at all stations. 

1.5.12                   Overall, there is no evidence indicating any unacceptable environmental impacts to sediment quality as a result of the contaminated mud disposal operations at ESC CMP Vd in December 2019.  Statistical analysis will be undertaken and presented in the corresponding quarterly report to investigate whether there are any unacceptable impacts in the area caused by the contaminated mud disposal.

1.5.13                         Pit Specific Sediment Chemistry of ESC CMP Vd December 2019

1.5.14                   Monitoring locations for Pit Specific Sediment Chemistry for ESC CMP Vd are shown in Figure 1.3.  A total of six (6) monitoring stations were sampled on 16 December 2019.  It is noted that one of the sample replicates collected at Active-Pit station ESC-NPAA showed abnormally high readings and thus it was considered as an outlier and excluded in the result presentation.

1.5.15                   The concentrations of most inorganic contaminants were lower than the LCEL at most stations, except for Copper having concentrations higher than LCEL at Active-Pit station ESC-NPAA (Figures 6 and 7 of Annex C). 

1.5.16                   Considering that the higher levels of Copper occurred within Active-Pit station ESC-NPAA only but not at the Pit-Edge and Near-Pit stations, there is no evidence indicating any unacceptable environmental impacts to sediment quality as a result of the contaminated mud disposal operations at ESC CMP Vd in December 2019.   

1.5.17                   For organic contaminants, the concentrations of TOC were lowest at Pit-Edge stations and were highest at Active-Pit stations in December 2019 (Figure 8 of Annex C).  The concentrations of TBT were generally similar across all stations, except it was higher at Active-Pit stations ESC-NPAA in December 2019 (Figure 9 of Annex C).  PCBs, DDT and DDE concentrations were below the limit of reporting at all stations.  The concentrations of Low Molecular Weight and High Molecular Weight PAHs were below LCEL at all the stations and were higher at Active-Pit Stations ESC-NPAA and ESC-NPAB. (Figure 10 of Annex C).

1.5.18                   There is no evidence indicating any unacceptable environmental impacts to sediment quality as a result of the contaminated mud disposal operations at ESC CMP Vd in December 2019.  Statistical analysis will be undertaken and presented in the corresponding quarterly report to investigate whether there are any unacceptable impacts in the area caused by the contaminated mud disposal.

1.5.19                         Impact Water Quality Monitoring during Dredging Operations of ESC CMP Vb December 2019

1.5.20                   Dredging operation at ESC CMP Vb commenced on 11 November 2019 and was completed on 5 December 2019.  Water quality monitoring during dredging operations was conducted on 2 and 4 December 2019 during the reporting period.  During each survey day, monitoring was conducted during both mid-ebb and mid-flood tides at two Reference (Upstream) stations and five Impact (Downstream) stations around the dredging operations at ESC CMP Vb.  Monitoring was also conducted at one Sensitive Receiver station situated in Ma Wan.  A total of eight (8) stations were monitored and locations of the sampling stations are shown in Figure 1.4

1.5.21                   Monitoring results are presented in Table B3 of Annex B.  Daily dredging volume in December 2019 is reported in Annex D.  Levels of DO, Turbidity and SS complied with the Action and Limit Levels (see Table B1 of Annex B for details).  The results indicated that the dredging operations at ESC CMP Vb did not appear to cause any unacceptable deterioration in water quality during this reporting period.  Therefore, no further action, except for those recommended in the Environmental Permit (EP-312/2008/A), are considered necessary for the dredging operations.

 

1.6                                Activities Scheduled for the Next Month

1.6.1                     The following monitoring activities will be conducted in the next monthly period of January 2020 for ESC CMP V (see Annex A for the sampling schedule ([6])

             Water Column Profiling of ESC CMP Vd;

             Routine Water Quality Monitoring of ESC CMPs;

             Pit Specific Sediment Chemistry of ESC CMP Vd; and

             Demersal Trawling for ESC CMPs.

1.7                                Study Programme

1.7.1                     A summary of the Study Programme is presented in Annex E.


([1])   ERM (2013)  FinalReport.  Submitted under Agreement No. CE 4/2009 (EP) Environmental Monitoring and Audit for Contaminated Mud Pit at East Sha Chau. For CEDD.

([2])   ERM (2017)  FinalReport.  Submitted under Agreement No. CE 23/2012 (EP) Environmental Monitoring and Audit for Contaminated Mud Pits to the South of The Brothers and at East Sha Chau (2012 - 2017). For CEDD.

([3])   http://epic.epd.gov.hk/EPICRIVER/marine/?lang=en

([4])   Sewell RJ (1999) Geochemical Atlas of Hong Kong. Geotechnical Engineering Office, Government of the Hong Kong Special Administrative Region

([5])   Whiteside PGD (2000) Natural geochemistry and contamination of marine sediments in Hong Kong. In: The Urban Geology of Hong Kong (ed Page A & Reels SJ). Geological Society of Hong Kong Bulletin No. 6, p109-121

([6])   The scheduled EM&A Programme for SB CMPs was completed in December 2018.